U.S. patent number 8,409,726 [Application Number 12/475,764] was granted by the patent office on 2013-04-02 for printed circuit board with multiple metallic layers and method of manufacturing the same.
This patent grant is currently assigned to Samsung Techwin Co., Ltd.. The grantee listed for this patent is Sung-il Kang, Se-chuel Park, Chang-han Shim. Invention is credited to Sung-il Kang, Se-chuel Park, Chang-han Shim.
United States Patent |
8,409,726 |
Shim , et al. |
April 2, 2013 |
Printed circuit board with multiple metallic layers and method of
manufacturing the same
Abstract
Provided is a printed circuit board (PCB) with multiple metallic
layers and a method of manufacturing the PCB to improve adhesion
between a metal film and a polymer film, on which a circuit pattern
is formed. The PCB includes: a first metal film; a polymer film
formed on one surface of the first metal film; and a second metal
film, interposed between the first metal film and the polymer film,
having a first surface facing the first metal film and a second
surface facing the polymer film, wherein the second surface is
rougher than the first surface.
Inventors: |
Shim; Chang-han (Changwon,
KR), Kang; Sung-il (Changwon, KR), Park;
Se-chuel (Changwon, KR) |
Applicant: |
Name |
City |
State |
Country |
Type |
Shim; Chang-han
Kang; Sung-il
Park; Se-chuel |
Changwon
Changwon
Changwon |
N/A
N/A
N/A |
KR
KR
KR |
|
|
Assignee: |
Samsung Techwin Co., Ltd.
(Changwon, KR)
|
Family
ID: |
42164147 |
Appl.
No.: |
12/475,764 |
Filed: |
June 1, 2009 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20100116528 A1 |
May 13, 2010 |
|
Foreign Application Priority Data
|
|
|
|
|
Nov 13, 2008 [KR] |
|
|
10-2008-0112865 |
|
Current U.S.
Class: |
428/675; 428/618;
428/680; 428/668; 428/669; 361/751; 428/209 |
Current CPC
Class: |
C25D
5/627 (20200801); C25D 5/12 (20130101); C25D
5/605 (20200801); H05K 3/384 (20130101); H05K
1/0393 (20130101); Y10T 428/12861 (20150115); Y10T
428/12944 (20150115); H05K 2201/0355 (20130101); H05K
2203/0307 (20130101); Y10T 428/12868 (20150115); Y10T
428/24917 (20150115); H05K 1/0346 (20130101); Y10T
428/12514 (20150115); Y10T 428/1291 (20150115); H05K
2203/0723 (20130101); H05K 2201/0154 (20130101) |
Current International
Class: |
B32B
15/20 (20060101) |
Field of
Search: |
;428/209,901,607,618,668,669,675,680 ;361/751 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
2005-353918 |
|
Dec 2005 |
|
JP |
|
1020030039937 |
|
May 2003 |
|
KR |
|
1020060109122 |
|
Oct 2006 |
|
KR |
|
Other References
Search Report established for JP 2009-258564 (Jul. 3, 2012). cited
by applicant.
|
Primary Examiner: Lam; Cathy
Attorney, Agent or Firm: Drinker Biddle & Reath LLP
Claims
What is claimed is:
1. A printed circuit board (PCB) comprising: a first metal film
where a circuit pattern is formed; a polymer film formed on one
surface of the first metal film; and a second metal film,
interposed between the first metal film and the polymer film,
having a first surface facing the first metal film and a second
surface facing the polymer film, wherein the second surface is
rougher than the first surface, wherein the second metal film is
formed of pure nickel.
2. The PCB of claim 1, wherein the first metal film is formed of
copper or a copper alloy.
3. The PCB of claim 1, further comprising a third metal film
interposed between the polymer film and the second surface.
4. The PCB of claim 3, wherein the third metal film is formed of
nickel, palladium, gold, or an alloy of nickel, palladium or
gold.
5. The PCB of claim 1, wherein the second metal film is formed on
the first metal film before the polymer film is formed on the one
surface of the first metal film.
6. The PCB of claim 1, wherein the second surface has a roughness
in a range between 0.2 and 0.8 gloss units.
7. The PCB of claim 1, wherein the second metal film has a
thickness in a range between 0.1 and 0.5 microns.
8. A printed circuit board (PCB) comprising: a first metal film
where a circuit pattern is formed; a polymer film formed on one
surface of the first metal film; a second metal film, interposed
between the first metal film and the polymer film, having a first
surface facing the first metal film and a second surface facing the
polymer film, wherein the second surface is rougher than the first
surface, wherein the second metal film is formed of a nickel alloy;
and a third metal film interposed between the polymer film and the
second surface, wherein the third metal film is a solid metal
layer.
9. A printed circuit board (PCB) comprising: a first metal film
where a circuit pattern is formed; a polymer film formed on one
surface of the first metal film; a second metal film, interposed
between the first metal film and the polymer film, having a first
surface facing the first metal film and a second surface facing the
polymer film, wherein the second surface is rougher than the first
surface, wherein the second metal film is formed of a nickel alloy;
and a third metal film interposed between the polymer film and the
second surface, wherein the third metal film is formed of nickel,
palladium, gold, or an alloy of nickel, palladium or gold.
Description
CROSS-REFERENCE TO RELATED PATENT APPLICATION
This application claims the benefit of Korean Patent Application
No. 10-2008-0112865, filed on Nov. 13, 2008, in the Korean
Intellectual Property Office, the disclosure of which is
incorporated herein in its entirety by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a printed circuit board (PCB) and
a method of manufacturing the PCB and more particularly, to a PCB
having improved adhesion between a metal thin film and a resin
material, and a method of manufacturing the PCB.
2. Description of the Related Art
Printed circuit boards (PCB) are essential in various electronic
and machine equipments.
The PCB is formed by attaching a copper foil onto one side or both
sides of a polymer insulating board formed of epoxy or polyimide,
and circuits are formed on the copper foil by etching or
plating.
Various attempts at improving adhesion between the copper foil and
the polymer insulating board have been developed.
One method of improving adhesion includes strengthening adhesion
between a polymer resin and the copper foil by coating the surface
of the copper foil with a polar polymer. However, since such a
method depends on chemical coupling, there is a limit to how much
the adhesion is improved. In addition, in a cross-linking process
performed on the polar polymers at a high temperature, internal
pressure is generated as organic compounds evaporate, thereby
forming defects, such as bubbles.
Another method involves physically or chemically forming nodules on
the surface of the copper foil, thereby improving adhesion between
the copper foil and the polymer resin through an uneven
surface-structure of nodules. Widely used methods of forming
nodules on the surface of the copper foil include jet scrubbing,
brush grinding, and soft etching. However, in the soft etching,
since the nodules have a thickness of about 1-2 .mu.m, the circuit
has a non-uniform width and etching linearity deteriorates. Also,
after the nodules are formed, an oxide film is formed on the
surface of the copper foil so that a process of removing the oxide
film is needed.
SUMMARY OF THE INVENTION
The present invention provides a printed circuit board (PCB) having
improved adhesion between a polymer film and a metal thin film on
which a circuit pattern is formed, and a method of manufacturing
the PCB.
According to an aspect of the present invention, there is provided
a printed circuit board (PCB) including: a first metal film; a
polymer film formed on one surface of the first metal film; and a
second metal film, interposed between the first metal film and the
polymer film, having a first surface facing the first metal film
and a second surface facing the polymer film, wherein the second
surface is rougher than the first surface.
The first metal film may be formed of copper or a copper alloy.
The second metal film may be formed of nickel or a nickel
alloy.
The PCB may further include a third metal film interposed between
the polymer film and the second surface.
The third metal film may be formed of nickel, palladium, gold, or
an alloy thereof.
According to another aspect of the present invention, there is
provided a method of manufacturing a printed circuit board (PCB),
the method including: preparing a first metal film; forming a
second metal film on one surface of the first metal film using
electroplating, the second metal film having a first surface
contacting the first metal film and a second surface opposite to
the first surface, wherein the second surface is rougher than the
first surface; and forming a polymer film on the second surface of
the second metal film.
The first metal film may be formed of copper or a copper alloy.
The second metal film may be formed of nickel or a nickel
alloy.
The electroplating may be performed for 3-20 seconds at a current
density of 10 A/dm.sup.2 or greater.
In the forming of the second metal film by using electroplating, a
plating bath including 2.5-3.5 g/l of nickel sulfate or nickel
chloride may be used.
The method may further include forming a third metal film on the
second surface of the second metal film before the forming of the
polymer film, wherein the polymer film is formed on the third metal
film.
The third metal film may be formed of nickel, palladium, gold, or
an alloy thereof.
In accordance with an embodiment of the method of the present
invention, the second layer is formed on the first layer before a
polymer is laid down.
According to the present invention, the adhesion between the first
metal film and the polymer film may be improved due to a simplified
manufacturing process.
Also, the diffusion preventing layer is formed so that reliability
and adhesion at a high-temperature and in a hygroscopic environment
may be improved.
BRIEF DESCRIPTION OF THE DRAWINGS
The above and other features and advantages of the present
invention will become more apparent by describing in detail
exemplary embodiments thereof with reference to the attached
drawings in which:
FIG. 1 is a cross-sectional diagram of a printed circuit board
(PCB) according to an embodiment of the present invention;
FIG. 2 is a cross-sectional diagram of a PCB according to another
embodiment of the present invention;
FIGS. 3 and 4 are cross-sectional diagrams illustrating a method of
manufacturing a PCB according to another embodiment of the present
invention;
FIG. 5 is a cross-sectional diagram of a PCB according to another
embodiment of the present invention;
FIG. 6 is a cross-sectional diagram of a PCB according to another
embodiment of the present invention; and
FIG. 7 is a scanning electron microscope (SEM) photograph of a
second surface.
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described more fully
with reference to the accompanying drawings, in which exemplary
embodiments of the invention are shown.
FIG. 1 is a cross-sectional diagram of a printed circuit board
(PCB) according to an embodiment of the present invention.
Referring to FIG. 1, the PCB according to the present embodiment
includes a first metal film 10, a second metal film 20, and a
polymer film 40.
The first metal film 10 is formed of copper or a copper alloy and
corresponds to a conductive layer, on which a circuit pattern is
formed.
The polymer film 40, formed of polyimide or acrylic resin, is
formed to face the first metal film 10.
The second metal film 20 is interposed between the first metal film
10 and the polymer film 40 and is formed of nickel or a nickel
alloy.
The second metal film 20 includes a first surface 21 facing the
first metal film 10 and a second surface 22 facing the polymer film
40.
The second metal film 20 may be formed on the first metal film 10
using electroplating. Here, the surface of the second surface 22
may be rougher than the surface of the first surface 21.
The polymer film 40 is formed on the second surface 22 of the
second metal film 20 so as to cover the second surface 22.
Since the second surface 22 contacting the polymer film 40 is
rough, adhesion between the polymer film 40 and the second metal
film 20 is improved. In addition, the second metal film 20 closely
adheres to the first metal film 10 due to the electroplating so
that adhesion between the first metal film 10 and the polymer film
40 may be improved by the second metal film 20.
Accordingly, since the second metal film 20 having the rough
surface is formed on the first metal film 10, the adhesion between
the polymer film 40 and the first metal film 10 may be simply
improved.
The PCB described above is manufactured as follows.
Firstly, the first metal film 10 formed of copper or a copper alloy
is prepared.
Then, the second metal film 20 is formed on one side of the first
metal film 10, that is, the upper surface of the metal thin film 10
as viewed in FIG. 1, by using electroplating. Here, the second
metal film 20 is formed to be a rough plating layer. Thus, as
described above, the second surface 22 formed opposite to the first
surface 21 contacting the first metal film 10 is electroplated to
be rough.
Here, the second metal film 20 may be formed of nickel or a nickel
alloy.
The composition of a nickel plating bath for forming a rough
plating layer as in the second metal film 20 may include 2.5-3.5
g/l of nickel sulfate or nickel chloride, 2.5-3.0 g/l of ammonium
sulfate, 4.5-5.0 g/l of sodium sulfate, 1.5-2.0 g/l of sodium
chloride, and 2.0-3.0 g/l of boric acid. In the composition of the
plating bath for forming the rough plating layer as in the second
metal film 20, nickel sulfate or nickel chloride may have a low
concentration of 10% or less of the composition of the plating bath
for forming a general nickel plating layer.
Also, electricity flows in the low concentrated plating bath with a
higher current density than when conventionally forming a general
nickel plating layer so that crystal growth of nickel may rapidly
have a rough surface at a low density.
More specifically, a high current density of 10 ASD (A/dm.sup.2) or
greater is applied to the plating bath with the composition
described above so that the second metal film 20, which is a nickel
plating layer having a rough surface, is formed. Also, the plating
process may be a reel-to-reel type which provides the first metal
film 10, rolled to one side of a roller, to the plating bath, the
first metal film 10 being rolled to the other side of the roller
after plating is completed. In order to increase the speed of
nickel plating and to stably obtain a rough nickel plating layer, a
high current density of 50 ASD may be applied. A plating process
time may take 3-20 seconds. During a plating process time of 3
seconds or below, growth of nickel crystal does not occur. When the
plating process time is 20 seconds or greater, secondary
contamination such as smut may occur on the rough nickel plating
layer due to excessive growth of nickel crystal.
The second metal film 20 formed of the rough nickel plating layer
may have a thickness of 0.1-0.5 .mu.m. When the second metal film
20 has a thickness of 0.1 .mu.m or below, efficiency of the rough
plating layer may be low and when the second metal film 20 has a
thickness of 0.5 .mu.m or greater, the plating layer may be
exfoliated due to excessive growth of nickel plating. That is,
growth of nickel in a vertical direction is insignificant in a
plating layer having a thickness of 0.1 .mu.m or below and the
plating layer having a thickness of 0.5 .mu.m or greater may be
separated due to excessive growth in a vertical direction.
FIG. 7 is a scanning electron microscope (SEM) photograph of the
second surface 22 of the second metal film 20 included in the PCB
according to an embodiment of the present invention. As illustrated
in FIG. 7, since the surface of the second surface 22 is rough,
adhesion between the second surface 22 and a polymer resin, which
naturally occurs due to surface roughness, is added after the
polymer resin is attached to the second surface 22 when forming the
polymer film 40, thereby improving adhesion between the polymer
film 40 and the second metal film 20.
After the second metal film 20 is manufactured, whether the second
surface 22 has a desired surface roughness may be examined by a
scanning electron microscope (SEM). However, time for the
examination is needed, and thus, methods of rapidly identifying
surface roughness during the process are needed.
Accordingly, gloss testing may be used. That is, when the gloss of
the second surface 22 is in the range of about 0.2 to 0.8, it is
regarded that the second metal film 20 having a desired surface
roughness is manufactured. In a gloss of 0.2 or below, roughness is
excessively achieved so that the polymer resin forming the polymer
film 40 may run over during the forming of the polymer film 40 and
a secondary quality problem such as resin bleed overflow (RBO) may
be generated. In gloss of 0.8 or greater, roughness is not
sufficiently achieved and thus a moisture sensitivity level (MSL)
is not improved.
After the second metal film 20 is formed, a precursor of a
polyimide monomer is cast on the second surface 22 of the second
metal film 20 and then, the polymer film 40 formed of polyimide may
be formed by cross-linking at a high temperature.
In conventional chip on film (COF) manufacturing, a seed layer such
as nickel or chrome is formed on a polyimide film using sputtering
and then is copper plated, thereby forming a copper foil. However,
in the present embodiment, the second metal film 20 having a rough
surface is firstly formed on the copper foil, that is, the first
metal film 10 by electroplating and then, the polymer film 40 is
formed on the second metal film 20 as described above. Thus, the
adhesion between the metal thin film 10 and the polymer film 40 may
be improved, and productivity and manufacturing costs may be
improved due to a simplified manufacturing process.
As illustrated in FIG. 2, the second metal film 20 and the polymer
film 40 are sequentially formed on both surfaces of the first metal
film 10 using the process described above so that the PCB may be
formed using films in which the outer surfaces are insulated.
FIGS. 3 and 4 are cross-sectional diagrams illustrating a method of
manufacturing a PCB according to another embodiment of the present
invention.
As in FIG. 3, second metal films 20 and 20' are respectively formed
on the surfaces of first metal film 10 and 10' by using rough
plating and then, second surfaces 22 and 22' of the second metal
films 20 and 20' are disposed to face each other.
Then, as in FIG. 4, a precursor of a polyimide monomer is cast
between the second surfaces 22 and 22', which face each other, and
the polymer film 40 formed of polyimide is formed by cross-linking
at a high temperature.
In this case, while the polymer film 40 is disposed at the center,
the first metal films 10 and 10' for forming a circuit pattern may
be disposed on both sides of the polymer film 40.
Also, in the present embodiment, the second metal films 20 and 20'
are respectively plated on both sides of the first metal films 10
and 10' and then the polymer film 40 is formed on the second metal
films 20 and 20' as in FIG. 2. Thus, as illustrated in FIG. 5,
while the polymer film 40 is disposed at the center, the first
metal films 10 and 10' for forming a circuit pattern are disposed
on both sides of the polymer film 40 and then the polymer films 40
may be formed to cover the outer surfaces of the first metal films
10 and 10', thereby manufacturing a multi-layered PCB.
FIG. 6 is a cross-sectional diagram of a PCB according to another
embodiment of the present invention.
Referring to FIG. 6, the second metal film 20 is formed on one
surface of the first metal film 10 using rough plating as in FIG. 1
and then, a third metal film 30 is formed on the second surface 22
of the second metal film 20. Then, the polymer film 40 is formed on
the third metal film 30.
The third metal film 30 may be formed of nickel (Ni), palladium
(Pd), gold (Au), or an alloy thereof and may function as a
diffusion preventing layer for preventing a metal component of the
first metal film 10 from being diffused in the polymer film 40
during forming of the polymer film 40, that is, for preventing the
metal component of the first metal film 10 from being diffused in
the interface between the polymer film 40 and the second metal film
20 and thereby, preventing adhesion between the polymer film 40 and
the second metal film 20 from deteriorating. In other words, since
the third metal film 30 is interposed between the polymer film 40
and the second metal film 20, a metal component of the first metal
film 10 is prevented from being diffused so that reliability and
adhesion at a high-temperature and in a hygroscopic environment may
be improved.
The third metal film 30 is not formed by the rough plating as in
the second metal film 20. Instead, the third metal film 30 may be
formed using a conventional plating process. Accordingly, a plating
bath with a higher density than that of the plating bath for
forming the second metal film 20 is used to form the third metal
film 30 and the third metal film 30 is plated at a low current
density.
Since the third metal film 30 is formed on the second surface 22
having the rough surface, the third metal film 30 may be formed to
be thin so that roughness of the second surface 22 is applied to
the third metal film 30.
The third metal film 30 may have a thickness of 0.1-0.5 .mu.m. When
the third metal film 30 has a thickness of 0.1 .mu.m or below, the
third metal film 30 may not function as a diffusion preventing
layer. When the third metal film 30 has a thickness of 0.5 .mu.m or
greater, the rough surface is not formed on the third metal film
30, thereby decreasing the adhesion between the third metal film 30
and the polymer film 40.
As in FIG. 6, the third metal film 30 may be formed as a single
layer. However, the present invention is not limited thereto and
the third metal film 30 may be formed as multiple layers.
The third metal film 30 may be also formed in the PCB illustrated
in FIGS. 2-5.
Experimental Example
A first metal film formed of a copper alloy is prepared.
A current density of 20 ASD flows in a plating bath including 3.5
g/l of nickel sulfate, 2.75 g/l of ammonium sulfate, 4.75 g/l of
sodium sulfate, 1.75 g/l of sodium chloride, and 2.5 g/l of boric
acid, and the first metal film is filled in the plating bath so as
to be plated for 20 seconds.
As illustrated in FIG. 7, a second surface of a second metal film
formed in the plating bath is rough enough that adhesion between
the second surface and a polymer film may be improved.
A precursor of a polyimide monomer is cast on the second surface of
the second metal film and then, is cross-linked at a temperature of
450.degree. C., thereby forming the polymer film.
According to the present invention, hard PCBs and soft PCBs used in
various electric, mechanical, and electronic equipments may be
manufactured. More specifically, the method of manufacturing the
PCB according to the present invention may be useful in
manufacturing casting type flexible copper clad laminates (FCCL),
in which fine pitch patterned circuits are formed by etching.
While the present invention has been particularly shown and
described with reference to exemplary embodiments thereof, it will
be understood by those of ordinary skill in the art that various
changes in form and details may be made therein without departing
from the spirit and scope of the present invention as defined by
the following claims.
* * * * *